A new alert about “dangerous” overcrowding at Euston station has been issued by the capital’s passenger watchdog.London TravelWatch called for a review “as a matter of urgency” after passengers were locked out of the station during the rush hour last Thursday evening in a desperate bid to limit the number waiting on the concourse.TravelWatch also warned that plans for new train services, including a new route between London and Stirling, “will only worsen” the problems at Euston.And it said it was “incredible” that the rail regulator, the Office of Rail and Road, was not continuing to press Network Rail, which owns Euston, to improve the situation after issuing it with an improvement notice a year ago.